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Sunday, October 15, 2006

Targeted Vaccinations Could Save Ethiopian Wolves

GLASGOW, Scotland, October 12, 2006 (ENS) - Specific groups of Ethiopian wolves must be targeted for rabies vaccination in order to prevent the world's rarest carnivore from the infectious disease, scientists said Wednesday. Rabies nearly drove the Ethiopian wolf to extinction in the 1990s and conservationists fear future outbreaks could wipe out the species entirely.

"Theoreticians have devoted a lot of effort to working out how to vaccinate populations in ways that prevent epidemics getting started, but this requires coverage that is impractical in wild populations," said lead author Dan Haydon, a University of Glasgow scientist. "We've looked at vaccination studies that don't prevent all outbreaks, but do reduce the chances of really big outbreaks - ones that could push an endangered population over the extinction threshold. These strategies turn out to be effective and a lot more practical.'

The study, published in the journal "Nature," suggests that vaccinating 30 percent of the wolf population that comes most in contact with domestic dogs would prevent a widespread outbreak of the disease.

The findings are important for a species at major risk of extinction. Found in the Bale Mountains of Ethiopia, the species is at risk from habitat destruction, but rabies has proven a more imminent threat.

First exposed to rabies via contact with domestic dogs, the wolves suffered an outbreak in the 1990s that killed nearly 75 percent of the population. Another outbreak in 2003 hit the species hard, leaving only about 500 wolves spread across six subpopulations.

In the wake of the 2003 outbreak, an emergency vaccination program was introduced. Analysis of that program by Haydon and other British researchers with the Ethiopian Wolf Conservation Program (EWCP), suggests that a targeted vaccination program is a far more effective strategy that a blanket vaccination effort.

Blanket vaccinations are too difficult because the wolves live in remote, inaccessible mountain enclaves.

The alternative strategy adopted by the EWCP is an effective reactive response to outbreaks, whereby Ethiopian wolves living in the mountain valleys close to infected packs are targeted.

The researchers suggest that in the event of a single suspected case, monitoring should be intensified and once two rabid carcasses are found, vaccination teams should be dispatched to target subpopulations living in connecting valleys.

Additional measures, such as vaccinating between 10 and 40 per cent of wolves in affected packs, if targeting the particularly large and highly connected packs, can further reduce overall mortality due to these outbreaks.

"We have shown that the vaccination of Ethiopian wolves, when appropriately and strategically used, is a safe, direct and effective method of reducing extinction threats," said coauthor Karen Laurenson, a University of Edinburgh researcher. "With the advent of new generations of oral vaccines, such methods are becoming ever more feasible and cost-effective."

The researchers note that vaccination of domestic dogs is also critical to protecting the wolves.

"Canid diseases, such as rabies and distemper, transmitted from domestic dogs pose the most immediate threat to their persistence, and targeted reactive vaccination intervention presents a useful tool to protect the remaining small wolf populations from extinction," said Dr Claudio Sillero-Zubiri, from Oxford University's Wildlife Conservation Research Unit (WildCRU).

Researchers with the WildCRU have been studying the wolves for two decades and in 1995 established the EWCP to address the most urgent threats to the species' survival.

"The WildCRU's aim is to put innovative science to practical use," said WildCRU Director David Macdonald. "These discoveries would have been impossible without long-term field-studies, and they show how cutting-edge science can have down-to-earth practical significance both for the protection of a very rare, and spectacular, wild species, and also for human well-being."